1. Field of the Invention
The present invention relates to a radio communication apparatus and a communication control method for executing a handover from a first radio communication network to a second radio communication network employing a different radio communication scheme from that employed by the first radio communication network.
2. Description of the Related Art
In recent years, along with advancement of radio communication technologies, a radio communication apparatus connectable to multiple radio communication networks employing different radio communication schemes has been put in practical use.
Such a radio communication apparatus includes a media independent handover user (MIH user, or mobility manager) for managing mobility among multiple radio communication networks, and multiple link controllers for setting the radio communication networks and radio links respectively.
Moreover, it has been proposed that a media independent handover function unit (MIH function unit, or handover controller) for controlling a handover between the radio communication networks (in other words, a handover between systems) is provided between the mobility manager and the multiple link controllers in the aforementioned radio communication apparatus connectable to the multiple communication networks (for example, IEEE P802.21/D04.00 Draft IEEE Standard for Local and Metropolitan Area Networks: Media Independent Handover Services, LAN MAN Standards Committee of the IEEE Computer Society (hereinafter, referred to as Non-Patent Document 1)).
The method described in Non-Patent Document 1, however, has the following problems. Generally speaking, a higher layer entity such as the mobility manager or an application (IP phone, for example) is capable of determining degradation of quality of service (QoS) in the higher layer entity, but does not recognize the relationship between the degree of degradation and the communication quality of the radio link. For this reason, there is a problem that the radio communication apparatus cannot execute a handover at timing an appropriate for the communication quality of the radio link even though the radio communication apparatus is provided with the handover controller. Due to this problem, the quality of the application cannot be maintained adaptively.
For the purpose of solving the aforementioned problem, the mobility manager may set a communication quality threshold in the handover controller to have a value appropriate for the communication quality of the radio link. Such a mobility manager, however, needs to be developed in consideration of each of the radio communication networks in terms of the processing procedure from the determination of the communication quality of the radio link to the execution of the handover. The development of the mobility manager taking all of the radio communication networks into consideration as described above raises another problem that the cost for the mobility manager increases.